[no subject]

More concretely, cache_unlink_parent should iterate
cache_shadow_detach() over the list of shadowing entries (as a tweak,
there might be a flag which asks for not doing so).
I think this would settle renaming issues.
Similar mechanisms could be used to maintain groupwise namecache
attibutes in each member of the shadow group, not just at the head. This
way your greatest annoyances (including the API muck-up) could be
solved.
We could keep the locking mechanism as it is in my patch. That's
transparent to the users anyway.
What do you think?
Csaba